
    <!DOCTYPE html>
    <html lang="zh-CN">
    <head>
      <meta charset="UTF-8">
      <meta name="viewport" content="width=device-width, initial-scale=1.0">
      <title>当有一个服务eureka联系不上，另一个又要访问这个服务怎么办 - 交互式测验</title>
      <style>
        @import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@400;500;700&display=swap');
        
        body {
          font-family: 'Noto Sans SC', sans-serif;
          background-color: #f4f7f9;
          color: #333;
          display: flex;
          justify-content: center;
          align-items: center;
          min-height: 100vh;
          margin: 0;
          padding: 20px;
          box-sizing: border-box;
        }
        
        .main-wrapper {
            position: relative;
            width: 100%;
            max-width: 900px; /* Wider to accommodate buttons */
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .quiz-container {
          background-color: #ffffff;
          border-radius: 16px;
          box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
          width: 100%;
          max-width: 700px;
          overflow: hidden;
          z-index: 10;
        }

        .quiz-header {
          background-color: #4a90e2;
          color: white;
          padding: 20px 30px;
          text-align: center;
        }

        .quiz-header h1 {
          margin: 0;
          font-size: 24px;
          font-weight: 700;
        }
        
        .quiz-header p {
            margin: 5px 0 0;
            font-size: 14px;
            opacity: 0.9;
        }

        .quiz-body {
          padding: 30px;
        }

        .progress-bar {
            display: none; /* 隐藏进度条 */
            width: 100%;
            background-color: #e0e0e0;
            border-radius: 5px;
            height: 10px;
            margin-bottom: 20px;
        }

        #progress-indicator {
            height: 100%;
            width: 0%;
            background-color: #4caf50;
            border-radius: 5px;
            transition: width 0.3s ease;
        }

        #question-container {
          margin-bottom: 20px;
        }

        #question-text {
          font-size: 18px;
          font-weight: 500;
          line-height: 1.6;
          margin-bottom: 25px;
        }

        .options-list {
          list-style: none;
          padding: 0;
          margin: 0;
        }

        .option-item {
          background-color: #f8f9fa;
          border: 1px solid #dee2e6;
          border-radius: 8px;
          padding: 15px;
          margin-bottom: 12px;
          cursor: pointer;
          transition: background-color 0.2s ease, border-color 0.2s ease;
        }

        .option-item:hover {
          background-color: #e9ecef;
        }
        
        .option-item.selected {
            background-color: #d1e7fd;
            border-color: #4a90e2;
        }

        .quiz-footer {
          padding: 20px 30px;
          display: flex;
          justify-content: space-between; /* 将按钮分布在两侧 */
          align-items: center;
          min-height: 65px; /* Reserve space */
        }

        .nav-btn {
          background-color: #4a90e2;
          color: white;
          border: none;
          border-radius: 8px;
          padding: 10px 20px;
          font-size: 16px;
          font-weight: 500;
          cursor: pointer;
          transition: background-color 0.2s ease, transform 0.2s ease;
          box-shadow: 0 4px 12px rgba(0,0,0,0.15);
        }
        
        #next-btn {
            background-color: #28a745;
        }

        .nav-btn:hover {
          background-color: #357abd;
          transform: scale(1.05);
        }
        
        .nav-btn:disabled {
            background-color: #a0c3e8;
            cursor: not-allowed;
            opacity: 0.7;
        }

        #result-container {
            border-top: 1px solid #eee;
        }
        
        .result-box {
            border-radius: 8px;
            padding: 20px;
            margin-top: 20px;
        }
        
        .result-box.correct {
            background-color: #d4edda;
            border: 1px solid #c3e6cb;
            color: #155724;
        }

        .result-box.incorrect {
            background-color: #f8d7da;
            border: 1px solid #f5c6cb;
            color: #721c24;
        }
        
        .result-box h3 {
            margin-top: 0;
        }

        .explanation-text {
            margin-top: 15px;
            line-height: 1.7;
        }
        
        .source-text {
            font-style: italic;
            font-size: 14px;
            margin-top: 15px;
            color: #555;
        }

        
        .final-score-container {
            padding: 40px;
            text-align: center;
        }
        .final-score-container h2 {
            margin-top: 0;
            margin-bottom: 30px;
        }
        .score-summary {
            display: flex;
            justify-content: center;
            gap: 20px;
            margin-bottom: 40px;
            flex-wrap: wrap;
        }
        .score-card {
            background-color: #f8f9fa;
            border-radius: 12px;
            padding: 20px;
            width: 180px;
            box-shadow: 0 4px 12px rgba(0,0,0,0.05);
            border: 1px solid #e9ecef;
        }
        .score-card h3 {
            margin: 0 0 10px;
            font-size: 16px;
            font-weight: 500;
            color: #555;
        }
        .score-card p {
            margin: 0;
            font-size: 28px;
            font-weight: 700;
            color: #333;
        }
        .score-details table {
            width: 100%;
            font-size: 16px;
        }
        .score-details td {
            padding: 4px 0;
        }
        .score-details td:last-child {
            text-align: right;
            font-weight: 700;
        }
        .report-actions button {
            background-color: #fff;
            border: 1px solid #ccc;
            border-radius: 8px;
            padding: 12px 25px;
            font-size: 16px;
            cursor: pointer;
            margin: 0 10px;
            transition: background-color 0.2s ease, border-color 0.2s ease, transform 0.2s ease;
        }
        .report-actions button:hover {
            background-color: #f1f1f1;
            border-color: #bbb;
            transform: translateY(-2px);
        }
        .report-actions button.primary {
            background-color: #28a745;
            color: white;
            border-color: #28a745;
        }
        .report-actions button.primary:hover {
            background-color: #218838;
        }
        
        .hint-container {
            background-color: #e0f7fa;
            border: 1px solid #b2ebf2;
            border-radius: 8px;
            padding: 15px;
            margin-top: 20px;
            color: #006064;
            font-size: 15px;
            line-height: 1.6;
            display: none; /* 默认隐藏 */
        }
      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>当有一个服务eureka联系不上，另一个又要访问这个服务怎么办 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
            </div>
          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "根据文档，当一个Eureka Client无法连接到Eureka Server时，它主要依赖什么机制来继续发现其他服务？",
    "options": [
      "它会立即触发服务降级（Fallback）逻辑。",
      "它会使用存储在本地的缓存信息来获取服务实例列表。",
      "它会无限期地重试连接，直到Eureka Server恢复正常。",
      "它会向同一个网络中的其他客户端广播请求，以寻找服务。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出，Eureka Client内部实现了缓存机制。它会定期从Eureka Server拉取注册表并缓存在本地。当无法与Server通信时，Client会利用这份本地缓存来继续提供服务发现功能，这是保障在Server短暂故障时系统韧性的关键。",
    "source": "文档中「1. Eureka Client 的缓存机制」部分",
    "hint": "思考一下，为了提高效率和容错性，Eureka客户端会在本地保存什么信息？"
  },
  {
    "question": "在微服务调用失败的场景下，服务降级（Fallback）机制的核心目标是什么？",
    "options": [
      "确保请求被多次重试，以应对网络抖动等暂时性问题。",
      "将失败的请求放入消息队列，等待服务恢复后异步处理。",
      "提供一个预定义的替代响应，保证系统部分功能可用并提升用户体验。",
      "将请求路由到另一个健康的Eureka Server节点。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "服务降级（Fallback）机制的主要作用是在目标服务不可用或调用失败时，执行一个预先定义好的降级逻辑，例如返回一个默认值或友好的提示信息。这可以防止故障向上游蔓延（即雪崩效应），从而提高整个系统的容错能力。",
    "source": "文档中「3. 服务降级（Fallback）机制」部分",
    "hint": "当一条路不通时，提供另一条备用路径或提示，这种策略叫什么？文档中提到了 Hystrix 或 Resilience4j。"
  },
  {
    "question": "为了解决Eureka Server本身的单点故障问题，文档推荐的关键策略是什么？",
    "options": [
      "在每个微服务客户端上启用更强大的缓存。",
      "使用消息队列（如Kafka）来代替Eureka进行服务注册。",
      "部署多个Eureka Server节点并配置成高可用集群模式。",
      "为服务调用配置更长的重试间隔和次数。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档在“Eureka 的高可用配置”一节中明确指出，为了防止服务注册中心自身成为瓶颈或单点故障，最佳实践是在生产环境中部署一个由多个Eureka Server节点组成的集群。这样，即使某个节点失效，其他节点仍然可以提供服务注册与发现功能。",
    "source": "文档中「4. Eureka 的高可用配置」部分",
    "hint": "思考一下如何让一个重要的组件（比如Eureka Server）自身不因为一台服务器宕机而失效。"
  },
  {
    "question": "文档中提到的`@Retryable`注解和`@HystrixCommand(fallbackMethod = ...)`注解分别代表了哪两种不同的容错策略？",
    "options": [
      "前者用于异步调用，后者用于同步调用。",
      "前者实现重试机制处理暂时性故障，后者实现服务降级以应对持续性故障。",
      "两者都用于实现服务降级，只是实现框架不同。",
      "前者用于客户端负载均衡，后者用于服务注册。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档通过代码示例清晰地展示了这两种策略。`@Retryable`（来自Spring Retry）用于在操作失败时自动重新执行，适合处理网络抖动等短暂问题。而`@HystrixCommand`（来自Hystrix）则用于定义一个降级方法，当主逻辑失败或熔断器打开时，会执行该降级逻辑，提供一个备用响应。",
    "source": "文档中「2. 重试机制」和「3. 服务降级（Fallback）机制」部分",
    "hint": "一个策略是“再试一次”，另一个策略是“如果不行，就走B计划”。这分别对应了哪两个注解？"
  },
  {
    "question": "根据文档，在什么场景下，采用“异步调用和消息队列”是特别有效的策略？",
    "options": [
      "当调用方需要立即获得响应结果，且对延迟非常敏感时。",
      "当服务间的调用允许有一定延迟，且希望解耦服务依赖以提高系统弹性时。",
      "当Eureka Server集群发生网络分区，导致服务列表不一致时。",
      "当客户端首次启动，本地缓存为空，需要强制从Server获取数据时。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档指出，异步调用和消息队列的核心优势在于解耦。这种方式适用于那些不需要实时返回结果的业务场景。通过将请求放入队列，调用方不必等待服务方处理完成，即使服务方暂时不可用，请求也不会丢失，从而大大提高了系统的弹性和整体吞吐量。",
    "source": "文档中「5. 异步调用和消息队列」部分",
    "hint": "“这种方式可以解耦服务之间的直接依赖，即使目标服务暂时不可用，请求也不会立即失败...”"
  },
  {
    "question": "文档指出了Eureka Client缓存机制存在一个潜在风险，这个风险主要发生在什么时刻？",
    "options": [
      "在缓存数据过多，导致客户端内存溢出时。",
      "在缓存中的服务地址信息因未及时更新而过时。",
      "在服务刚启动，尚未从Server获取到任何缓存数据时。",
      "在网络非常稳定，缓存机制显得多余时。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "在“Eureka Client 的缓存机制”一节的“注意”部分，文档特别强调了这一点：该机制的前提是缓存已存在。如果一个服务刚刚启动，它的本地缓存是空的，此时如果Eureka Server恰好不可用，那么它就无法获取任何服务实例信息，导致服务发现失败。",
    "source": "文档中「1. Eureka Client 的缓存机制」部分",
    "hint": "考虑一个“冷启动”的场景，此时客户端本地什么信息都没有。"
  },
  {
    "question": "像Ribbon或Spring Cloud LoadBalancer这样的工具，在与Eureka配合使用时，其主要职责是什么？",
    "options": [
      "作为API网关，对外部请求进行统一鉴权和路由。",
      "作为服务注册中心，替代Eureka的功能。",
      "在客户端侧，根据从Eureka获取的服务列表进行动态路由和负载均衡。",
      "作为断路器，在服务调用失败时执行降级逻辑。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档在“动态路由和负载均衡”一节中介绍，Ribbon等工具是客户端负载均衡器。它们与Eureka协同工作：首先从Eureka获取一个服务的所有健康实例列表，然后根据预设的策略（如轮询）在客户端选择一个实例发起请求，从而将流量均匀分配到多个实例上。",
    "source": "文档中「6. 动态路由和负载均衡」部分",
    "hint": "当一个服务有多个实例时，如何智能地决定将请求发送到哪一个实例？"
  }
];
        console.log("Quiz Data:", JSON.parse(JSON.stringify(quizData))); // 添加这行用于调试，以可展开的JSON格式输出
        
        let currentQuestionIndex = 0;
        let score = 0;
        // 存储每个问题的回答状态
        const userAnswers = new Array(quizData.length).fill(null); 

        const questionTextEl = document.getElementById('question-text');
        const optionsListEl = document.getElementById('options-list');
        const resultContainerEl = document.getElementById('result-container');
        const quizContentEl = document.getElementById('quiz-content');
        const progressIndicatorEl = document.getElementById('progress-indicator');
        const prevBtn = document.getElementById('prev-btn');
        const nextBtn = document.getElementById('next-btn');
        const hintBtn = document.getElementById('hint-btn');
        const hintContainerEl = document.getElementById('hint-container');

        function loadQuestion() {
          resultContainerEl.innerHTML = '';
          optionsListEl.innerHTML = '';
          hintContainerEl.style.display = 'none'; // 隐藏提示
          
          if (currentQuestionIndex >= quizData.length) {
            showFinalScore();
            return;
          }

          updateProgress();

          const currentQuestion = quizData[currentQuestionIndex];
          questionTextEl.textContent = `(${currentQuestionIndex + 1}/${quizData.length}) ${currentQuestion.question}`;
          
          currentQuestion.options.forEach((optionText, index) => {
            const li = document.createElement('li');
            li.className = 'option-item';
            li.textContent = optionText;
            li.dataset.index = index; // Store index in a data attribute
            // 如果这道题已经回答过，恢复状态
            if (userAnswers[currentQuestionIndex] !== null) {
                if (index === userAnswers[currentQuestionIndex]) {
                    li.classList.add('selected');
                }
            }
            optionsListEl.appendChild(li);
          });

          // 如果已经回答过，直接显示结果
          if (userAnswers[currentQuestionIndex] !== null) {
              const isCorrect = userAnswers[currentQuestionIndex] === currentQuestion.correctAnswerIndex;
              showResult(isCorrect, currentQuestion);
          }
          
          updateNavigationButtons();
          updateProgress();
        }

        function selectOption(optionIndex) {
            userAnswers[currentQuestionIndex] = optionIndex;
            const currentQuestion = quizData[currentQuestionIndex];
            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

            // 重新计算分数
            score = userAnswers.reduce((acc, answer, index) => {
                return answer === quizData[index].correctAnswerIndex ? acc + 1 : acc;
            }, 0);

            showResult(isCorrect, currentQuestion);
            updateNavigationButtons();
        }
        
        function updateProgress() {
            const answeredQuestions = userAnswers.filter(answer => answer !== null).length;
            const progressPercentage = (answeredQuestions / quizData.length) * 100;
            progressIndicatorEl.style.width = `${progressPercentage}%`;
        }
        
        function updateNavigationButtons() {
            prevBtn.style.display = 'block';
            nextBtn.style.display = 'block';
            hintBtn.style.display = 'block'; // 显示提示按钮

            prevBtn.disabled = currentQuestionIndex === 0;
            nextBtn.disabled = false; // 最后一题时，下一题按钮不禁用，而是用于显示报告
            nextBtn.textContent = (currentQuestionIndex === quizData.length - 1) ? '查看报告' : '下一题';
            
            // 如果当前问题没有提示，则禁用提示按钮并隐藏提示内容
            if (!quizData[currentQuestionIndex].hint) {
                hintBtn.disabled = true;
                hintContainerEl.style.display = 'none';
                hintContainerEl.textContent = ''; // 清除旧的提示内容
            } else {
                hintBtn.disabled = false;
            }
        }

        function showResult(isCorrect, questionData) {
            resultContainerEl.innerHTML = ''; // 清空之前的结果
            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
            let html = `<h3>${isCorrect ? '回答正确！' : '回答错误'}</h3>`;
            if (!isCorrect) {
                html += `<p><strong>正确答案是：</strong> ${questionData.options[questionData.correctAnswerIndex]}</p>`;
            }
            html += `<div class="explanation-text">${questionData.explanation}</div>`;
            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
            resultBox.innerHTML = html;
            resultContainerEl.appendChild(resultBox);

            // 禁用所有选项的点击事件，并高亮正确/错误答案
            Array.from(optionsListEl.children).forEach((child, index) => {
                child.style.pointerEvents = 'none';
                // 高亮正确答案
                if (index === questionData.correctAnswerIndex) {
                    child.classList.add('correct'); // 需要添加CSS样式
                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
                }
                // 如果选错了，高亮错误选项
                if (!isCorrect && index === userAnswers[currentQuestionIndex]) {
                    child.classList.add('incorrect'); // 需要添加CSS样式
                    child.style.backgroundColor = '#f8d7da';
                    child.style.borderColor = '#f5c6cb';
                }
            });
        }

        function goToNextQuestion() {
            if (currentQuestionIndex < quizData.length - 1) {
                currentQuestionIndex++;
                loadQuestion();
            } else {
                showFinalScore();
            }
        }

        function goToPreviousQuestion() {
            if (currentQuestionIndex > 0) {
                currentQuestionIndex--;
                loadQuestion();
            }
        }
        
        function showHint() {
            const currentQuestion = quizData[currentQuestionIndex];
            if (currentQuestion.hint) {
                hintContainerEl.textContent = currentQuestion.hint;
                hintContainerEl.style.display = 'block';
            } else {
                hintContainerEl.style.display = 'none';
            }
        }

        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  